Gypsum plaster products and plaster-base material



C. K. SWIFT July 19, 1932 GYPSUM PLASTER PRODUCTS AND PLASTER BASE MATERIAL Filed Aug. 31, 1931 Patented July s, 1932 PATENT orrlca UNITED STATES CLEMENT K. SWIFT, OF IEHNBYLVANIA, ASSIGNOB TO llncmms &

FORBES COMPANY, OF GAIEDER, NEW JERSEY, A CORPORATION OF HEWJTERBEY GYPSUM PLASEER PRODUCTS AND BLASTEB-BASE Application fled August 31, 1881. Serial No. 560,519.

My invention relates to an improved product having a coating of gypsum plaster thereon, to a plasterbase material or novel and valuable properties, and to the method of roducingsaid products.

ee object of my invention is te provide a plaster base material for use plasters Which is characterized by its ability to induce a rapid set of plaster the plaster and plaster-base interface, the result that there is a reduction in the tram i'er of moisture from the moist plaster to the plaster-base material, resulting in less enpansion of the base material with accempmying freedom from we rping. V A further o ject of my invention is to furnish a plaster-base'materifl which, when i treated with 'sum plasters, provide a reinforcinglayer at the plaster and'plasterbase interface during the setting period, thus tendin to counteract stresses strains which ring about distortion of the plastertreated product.

Still another object of my invention is to 28 provide a plaster-base material, which, when treated with gypsum plaster, be free from the objectionable so-called dry-cu of the plaster, by which is meant that condition so often encountered where the mois- 30 ture fails to hydrate the gypsum complete- 1y, leaving a very weal: and crumbly layer as a bond between the main plamr body and the base material.

A further object of my invention is to provide a plaster base material which presents to the sum plaster a surface capable of protecting the rosin or other size employed in the fibre board or other base material from attack by the alkaline material contained in the plaster.

A further object of my invention is to provide a product having a coating of gypsum plaster thereon in which there is an exceptionally strong bond between the base material and the plaster, and which, therefore, is of great practical value and of wide applicability in the trade. 7

Other objects of my invention will be apparent from a consideration of the specifics W tion and claims.

plaster cut away to show the lnthe drawing:

Figure 1 is a perspective view of-the plaster base material with the coating of the gypsum plaster accelerator thereon; a

Figure 2 is a perspective view of the gypsum plaster product of the invention in one stage of its set or in the case where the accelerator f has not completely diffused through the plaster, with a section of the plaster base material with its coating of accelerator; and

Figure 3 is a view, similar to Figure 2, of the finished product where the accelerator has completely diflused through the plaster.

Heretoiore, in the use of gypsum plasters, dificulties have beenencountered when these materials are applied to base materials, due to the fact that the laster in contact with the base member ten to set relatively slowly. In many instances, the plaster at the interface dries out prior to complete hydration, and, therefore, the bond between the main plaster body and the base material is weak; consequently, the main plaster body oftentimes strips from the base material. Furthermore, in the use of gypsum lasters in conjunction with fibre boards an other absorbent base "materials, the relatively slow setting of the plaster at the interface allows the fibre board to absorb a large amount of moisture, resulting in warping of the board. In other instances, the fibre board which contains rosin or other size sensitive to alkaline materials is rendered less-effective, due to the action of the alkaline material in the gypsum plaster on the alkaline-sensitive sizing material.

My invention contemplates the presence terial which insures a rapid set of the gypsum plaster at the plaster and plaster-base inter face. The base member of the present invention is applicable for use with any type of gypsum plaster; for example, gypsum plaster may consist solely of dehydrated gypsum, that is, calcium sulphate containing one-half of a material at the surface of the base ma- Y molecule of water, or it may be composed of a mixture of dehydrated gypsum and lime. It may or may not contain retarders, such as alkaline compounds of organic materials, for

instance, gluei feathers or the like, dissolved in lime, and i desired, the gypsum mix itself may contain accelerators. The gypsum plaster, which is employed in a wet plastic '5 state, isapplied to t e ase material of the invention in the usual manner" in which gypsum plasters have previously been employed. My invention is characterized b i the pres. once at the surface of the plasterase'material, prior to the application of the gypsum ,plaster, of a gypsum plaster accelerator ca 1 pable of producing'a rapid set of gypsum at the plaster and lastcr=-base interface. The

accelerator ma e of a wide variety of materials, and suc accelerators are well known,

' and are now employed in gypsuln plaster 1 mixes to decrease the setting time thereof. As I am advised, however, such accelerators have always previously been mixed withthe gypsum plaster and have never been applied although it is to be understood that the rep cited compounds do not constitute a complete list Zinc acetate, zinc sulphate, cadmium s'u'lotassium bichro-L.

phate, copper .sulphate, 'mate, aluminum sulphate, erric chloride, po'- tassium sulphate, sodium sulphate,;magne-- sium sulphate, ferrous sulphate, chromium 0 sulphate, oxalic acid and hydrated gypsum,

c of water I particularly applicable, although "in certain cases the use of zinc acetate and of other of the compounds'is' desirable; The compounds may be intimately mixed with or distributed through the structure of the base material during manufacture, but preferably the coinrinted ion pounds are sprayed, painted or the surface intended to receivet e gypsum plaster. The water-soluble compounds are preferably dissolved in water prior to their application; for example, they may be emoyed in a 15% water solution. If hydrated um is used as the accelerator, itfmay bev 'amted on the'surface of the base material t'erial how deep the gypsum orator-penetrate the base material so long. as

the base material presentsasurface containing the accelerator at the time the plaster-[is applied thereto'. The amount of accelerator f%employedis li iicritical, and various amounts may be used, ;the exact amount depending.

as upon th leted a celerator, the partitlllu? cium sulphate containing two molecules plaster employed, the nature of' the base material, and the results desired.

The inveiition is articularly applicable for the treatment of fi re boards of the stand-' 'ard type which may be composed of wood one of the usual steps employed in finishing the board for the market. Fibre boards are normall thoroughly dried after their formation, an then sprayed with water to raise the moisture content thereof to' approximately 10%, which is the average water content of the air. The accelerator if soluble in water may be dissolved in the water employed to bring the moisture content of the fibre board up to the desired amount and applied by spraying the board with the accelerator solution in the same manner'as, has previously been employed with pure water.

The use of the novel gypsum plaster-base present invention insures amaterial of the rapid set of the laster at the plaster and plaster-base inter ace, thus providing a film of set plaster material which acts as a water seal to prevent the tra the unset portion of t e plaster to the plasterbase materials. There is also provided a reinforcing layer at the interface during the setting period of the main plaster body which layer, due to its strength, tends to resist distortional stresses. Both'of these factors conf tribute in preventing plaster-base material Of th1s group the metallic sulphatesarefrom warping and -buckling. The rapid set fer of the water from of the plaster at the interface also reduces the possibility of dry-out of the plaster at this point. us a bond is provided between the main plaster body and the plaster-base material, which is exceptionally strong and durable, and which may be of considerable depth.

The rapidset additionally protects any alkaline sensitive-size, such as rosin size which may be employed in the plasterbase material, from attac which is normally found in gypsum plasters. 'All of these advantages contribute torender by the alkaline material (lime) the products of the present invention of value 1 and wide a licabili in the ind 111 the form of a thin, coating. It is'immag f pp ty ustl'y laster accel-v Referring-to the drawing, the plaster base material is shown therein at 1 with a coating -2 of the sum plaster accelerator thereon. It is to be understood that in many instances,

absorbed. in the surface of the plaster .base material. In the';drawing, however, for the 'the coating of gypsum plaster accelerator will 7 not be visible .uponexamination. since it is v accelerator .has completely diffused through the 'ypsum plaster.

Mibst plaster bases contain metallic sulphates as a product of reaction of incorporated sizes. These sulphates are, however,

present only in extremely small quantities and are insulficient to produce any accelerating effect upon applied plasters. It will, therefore, be understood inemploying the phrase containing a soluble metallic sulphate in the appended claims, that this phrase applies to a sulphate content suflicient to effect acceleration.

Considerable modification is possible in the choice of accelerators emplo ed, in the amounts used, as well as in them method of application to the plaster-base material without departing from the essential features of my invention.

I claim: i 1. A gypsum plaster-base material containing at the surface thereof, a gypsum plaster accelerator capable of producing a rapidset of gypsum plaster at the plaster and plasterbas'e interface upon the application of gypsum plaster thereto.

2. A gypsum plaster-base material containing at the surface thereof a soluble metallic sulphate capable of producing a rapid set of gypsum plaster at the 'plaster and plasterbase interface upon the application of gyp sum plaster thereto. 3. A gypsum plaster-base material contain ing' at the surface thereof zinc sulphate,1 whereby a rapid set of the gypsum plaster at the plaster and plaster-base interface is pro-' vided upon the application of gypsum plaster. thereto. I

4. A gypsum plaster-base material containing at the surface thereof zinc acetate,

face thereof a soluble metallic sul hate capable of producing a rapid set of plaster at the plaster and plaster-base interface upon the application of gypsum plaster thereto. I

7. A gyipsum plaster-base material comprising a 'bre board containing at the surface thereof zinc sulphate, whereby a rapid set of the gypsum plaster at the laster and plaster-base interface is provide upon the application of gypsum plaster thereto.

8. A gypsum plaster-base material comprising a fibre board containing at the surface thereof zinc acetate, whereby a rapid set of the gypsum plaster at the plaster and plaster-base interface is provided upon the application of gypsum plaster thereto.

9. A, gypsum plaster product supported by a base material having an exceptionally 'stron bond therebetween caused by the rapid gypsum set 0 the gypsum plaster atnthe surface of the base material brought about by the reaction between the gypsum plaster and a gypsum plaster accelerator capable of producing a rapid set contained at the surface of the base member prior to the application of the gypsum plaster.

10. A-i" psum plaster product. supported board base material having an exceptionally strong bond therebetween caused by the rapid set of the gypsum laster at the surface of the base materia brought about by the reaction between the gypsum plaster and a gypsum plaster accelerator capabl'e of producing a rapid set contained at the surface of the base member prior to the application of the gypsum plaster.

11. A gypsum plaster-base material containing at the surface thereof sodium sulphate, whereby a rapid set of the gypsum plaster at the laster and laster-base interface is provi ed upon t e application of gypsummlaster thereto.

rising at fibre board containing at the surace t ereof sodium sulphate, whereby a rapid set of the gypsum plaster at the laster and plaster-base interface is provide upon the application of psum plaster thereto. C EMENT K. SWIFT.

whereby a rapid set of .the gypsum plaster at the plaster and plaster-base interface is provided upon the application of gypsum plaster, thereto. 9 Y

5. A gypsum plaster-base material comprising afibre board containing at the surface thereof, a gypsum plaster accelerator ca able of producing a rapid set of gypsum p aster at the plaster and plaster-base interface upon the application of gypsum plaster thereto.

6. A gypsum plaster-base material comprising a fibre board containing at the sur- 12. A gypsum plaster-base material com- 

